I have some experience with various tailors in BKK. First off, Crown Tailors is absolutely horrible quality. I had a look at their sample suits there and they are the worst I've seen anyplace. Avoid this place at all costs. Nothing but a total ripoff.

Rajawongse and Raja's seemed to be pretty equal to each other. Just your typical BKK Indian/Sikh Tailor geared for tourists who don't really know anything about quality. If you don't know anything about good fabric and good suit construction, you'll probably be happy with them. I honestly cannot recommend them but there are obviously a lot of happy customers, though I doubt any of those happy customers really know about quality custom made clothes. Neither of them have a good selection of better fabrics. Of course they'll tell you they have good quality fabric, but just calculating the price they charge will tell you their fabric is nothing but cheap local fabric. You won't find any fine Italian or Swiss cloth in their shops. I'd also add Pinky's Tailor to this group, though some would say he's a bit better than Rajawongse or Raja. He does have a slightly better selection of fabric, though being he can't even tell you what the fabric is means he's highly suspect in my opinion. All of the Indian/Sikh tailors I've seen aren't really tailors. They are just someone who measures you and takes your order/money. They send all their work out and don't really know the true ins-and-outs of tailoring. I had to laugh when I saw how the plump Indian guy in Raja's was dressed when I went into there. His clothes were really awful and a terrible advertisement for his business. The taller gentleman was better, but still not impeccably dressed as I'd expect from a tailor I'd use.

The best I can recommend in Bangkok is either July Tailor or Art's. Both nearby to Sala Daeng BTS Station. July Tailor does a lot of work for the Thai Royal Family and is a highly respected tailor with the Thai upper class, not a typical tourist tailor. Likewise with Art's, though they do a significant business with Japanese tourists as well as well-off Thais. This class of tailor has a good selection of higher end fabrics and based on everything I've heard and experienced deliver a good product, but at a price that many tourists will probably find too expensive. You will pay here several times what you would from the tourist tailors, but naturally you will be getting a suit of much higher quality construction and fabric as well.

In tailoring, as with everything else, you get what you pay for. Buy an inexpensive suit/tux from a tourist tailor and you will get nothing but a cheap suit that will not look very good and likely will not last. Buy an expensive suit from a real tailor, using quality fabrics and you will get something that looks great and will last much longer.

Tailors in the tourist areas of BKK are an infestation. They are everywhere. Most all of them advertising ridiculously low prices and for some reason tourists seem to think they are getting a good deal. The fabric alone for a good suit costs much more than what they are charging, so immediately that should send up a red flag. They are merely taking advantage of cheap sweat-shop labor in Thailand which will make your suit for almost nothing. The "tailor" supplies the low-quality fabric and makes a very handsome profit as there is a huge markup over his actual costs. That's why there's so many of these tailors in BKK. Always lots of gullible tourists who don't know how to tell the difference between a good tailor and a bad/fake tailor, nor the difference between a good suit and a cheap bad suit.